The effects of mindfulness-based stress reduction on
objective and subjective sleep parameters in women with breast cancer: a randomized controlled trial
Cecile A. Lengacher1*, Richard R. Reich2,3, Carly L. Paterson1, Heather S. Jim4, Sophia Ramesar1, Carissa B. Alinat1, Pinky H. Budhrani5, Jerrica R. Farias1, Melissa M. Shelton1, Manolete S. Moscoso1, Jong Y. Park6and Kevin E. Kip1
1College of Nursing, University of South Florida, Tampa, FL, USA
2College of Arts and Sciences, University of South Florida Sarasota-Manatee, Sarasota, FL, USA
3Biostatistics, Moffitt Cancer Center and Research Institute, Tampa, FL, USA
4Health Outcomes and Behavior Program, Moffitt Cancer Center and Research Institute, Tampa, FL, USA
5Dana Farber Institute, Harvard Medical School, Boston, MA, USA
6Cancer Epidemiology, Moffitt Cancer Center and Research Institute, Tampa, FL, USA
*Correspondence to:
College of Nursing, University of South Florida, 12901 Bruce B.
Downs Blvd., MDC Box 22, Tampa, FL 33612-4766, USA.
E-mail: clengach@health.usf.edu
Received: 31 October 2013 Revised: 12 May 2014 Accepted: 19 May 2014
Abstract
Objective: The purpose of this study was to investigate the effects of mindfulness-based stress reduc- tion for breast cancer survivors (MBSR(BC)) on multiple measures of objective and subjective sleep parameters among breast cancer survivors (BCS).
Methods: Data were collected using a two-armed randomized controlled design among BCS enrolled in either a 6-week MBSR(BC) program or a usual care (UC) group with a 12-week follow-up. The present analysis is a subset of the larger parent trial (ClinicalTrials.gov Identifier: NCT01177124). Seventy-nine BCS participants (mean age 57 years), stages 0–III, were randomly assigned to either the formal (in-class) 6-week MBSR(BC) program or UC. Subjective sleep parameters (SSP) (i.e., sleep diaries and the Pittsburgh Sleep Quality Index (PSQI)) and objective sleep parameters (OSP) (i.e., actigraphy) were measured at baseline, 6 weeks, and 12 weeks after completing the MBSR(BC) or UC program.
Results: Results showed indications of a positive effect of MBSR(BC) on OSP at 12 weeks on sleep efficiency (78.2% MBSR(BC) group versus 74.6% UC group, p = 0.04), percent of sleep time (81.0%
MBSR(BC) group versus 77.4% UC group,p = 0.02), and less number waking bouts (93.5 in MBSR (BC) group versus 118.6 in the UC group,p < 0.01). Small nonsignificant improvements were found in SSP in the MBSR(BC) group from baseline to 6 weeks (PSQI total score,p = 0.09). No significant relationship was observed between minutes of MBSR(BC) practice and SSP or OSP.
Conclusions: These data suggest that MBSR(BC) may be an efficacious treatment to improve objec- tive and subjective sleep parameters in BCS.
Copyright © 2014 John Wiley & Sons, Ltd.
Introduction
Sleep difficulties are a common, distressing problem that affects 38–56% of cancer survivors [1]. Sleep disturbance is a broad term that encompasses difficulties initiating and maintaining sleep, and, furthermore, individuals with sleep disturbance may or may not have a clinical diagnosis of insomnia or other sleep disorders. The prevalence of a clinical diagnosis of insomnia is highest in breast cancer survivors (BCS) (68%) [2,3], with symptoms persisting at least 2–5 years after treatment [4–6].
Sleep disturbances among survivors are associated with high levels of distress [7] and are often untreated or undertreated [8,9]. This is concerning because sleep disruption often contributes to fatigue, depression, poorer treatment outcomes [10], reduced quality of life (QOL) [11], and disrupted daily functioning [9,12]. Left unresolved, sleep problems may result in diminished
work productivity and increased health care utilization costs [13,14].
Mindfulness-based stress reduction
Mindfulness-based stress reduction (MBSR), a standard- ized stress reduction program that emphasizes mindful- ness meditation, has the potential to improve sleep [15].
Although cognitive behavioral therapy for insomnia is considered the gold standard nonpharmacological treat- ment for insomnia, it may not target the increased psycho- logical distress and fears of recurrence among cancer survivors [8,16,17]. MBSR for breast cancer survivors (MBSR(BC)), specifically adapted for BCS, has demon- strated reductions in distress, fatigue, depression, and fears of recurrence while improving drowsiness and sleep disturbance [18,19].
Use in cancer populations
The effects of MBSR on SSP among cancer survivors were examined in three randomized controlled trials (RCT) [19–21] and three uncontrolled trials [22–24]. These six studies showed that MBSR significantly improved measures of subjective sleep parameters (SSP). To date, however, no studies have examined the effects of MBSR on objective sleep parameters (OSP) in cancer survivors.
Use in noncancer populations
Subjective and objective measurements of sleep improve- ment after MBSR therapy have been documented in three RCT [27,29,30] and four uncontrolled trials [25,26,28,31]
of noncancer populations. Of the seven studies that examined SSP changes, six found significant improvements in SSP in the MBSR group [25–30]. Only one trial showed no improvement in SSP following MBSR therapy [31]. A systematic review found associations between the benefits of MBSR treatment, improved sleep quality, and decreased rumination, but because of limitations of the studies reviewed, the authors identified a need for additional well- designed controlled trials to confirm these associations [32].
Of the three studies [33–35] measuring changes in OSP in noncancer populations, one study found significant improvement following MBSR. An RCT compared MBSR with eszopiclone pharmaceutical therapy in 30 adults with primary insomnia and found similar improvements in total sleep time (TST) and sleep efficiency in both groups with the MBSR group having greater reductions in sleep onset latency [33]. In a study of 70 adults, MBSR improved SSP but did not improve OSP measures [34]. Similarly, MBSR improved SSP among adolescents with substance abuse problems, but actigraphy results were not significant (p = 0.06) [35].
The purpose of this study was to conduct a subset anal- ysis of the larger parent trial (ClinicalTrials.gov Identifier:
NCT01177124). We hypothesized that compared with the usual care (UC) group, participants who were randomly assigned to the MBSR(BC) program would experience greater improvements in SSP and OSP at 6 weeks and sustained improvements at 12 weeks. This postulated effect would enhance the clinical significance of MBSR (BC) and provide an additional evidence-based, nonpharmacological treatment to improve sleep.
Methods Participants
Seventy-nine participants were recruited for this study from Moffitt Cancer Center and Carol and Frank Morsani Center, located in Tampa, Florida. The sample was composed of individuals who met inclusion criteria and were enrolled in the parent study (Mindfulness-based
Stress Reduction (MBSR) Symptom Cluster Trial for Breast Cancer Survivors, ClinicalTrials.gov Identifier:
NCT01177124). The purpose of the parent study was three- fold: (i) to evaluate the efficacy of the MBSR(BC) program in improving psychological and physical symptoms, QOL, and measures of immune function and a stress hormone (cortisol); (ii) to test whether positive effects achieved from the MBSR(BC) program are mediated through changes in mindfulness and fear of recurrence of breast cancer; and (iii) to evaluate whether positive effects achieved from the MBSR(BC) program are modified by specific patient char- acteristics measured at baseline. The participants for this subset analysis were enrolled from January 1, 2010 to December 31, 2010, the budget period of the sleep supplement grant as part of the parent study (Figure 1). Inclusion criteria consisted of the following: (i) women aged 21 years or older;
(ii) a previous diagnosis of stage 0–III breast cancer (BC);
(iii) treatment of lumpectomy and/or a mastectomy; (iv) completed adjuvant radiation and/or chemotherapy between 2 weeks and 2 years prior to study enrollment;
and (v) English proficiency at the eighth-grade level.
Having sleep disturbance was not an inclusion criterion for participation in the trial. Individuals were ineligible if they had stage IV cancer, a current, severe psychiatric diagnosis as indicated by referring clinicians or a cancer recurrence.
Study design and randomization
A two-armed RCT randomized participants to either the MBSR(BC) program or the UC program. After participants were enrolled by assigned research staff, a computer- generated random number system was used to randomly assign subjects stratified by stage of cancer (stage 0 or I versus II or III) and types of treatment (lumpectomy versus mastectomy and radiation with or without chemo- therapy). With the randomization strata of type of surgery and type of BC treatment, subjects were randomly assigned to the two treatment arms in variables blocks of six and eight subjects, as provided by the project methodologist. To maintain allocation concealment, assignments were enclosed in a letter to the participant that was sequentially numbered and placed in an opaque sealed envelope by assigned research staff. Research personnel as well as participants were blinded to study assignment until after completion of baseline assessment.
The institutional review board at the University of South Florida approved the study protocol.
Recruitment and data collection procedures
Clinic nurses assisted in identifying eligible patients.
Those who met inclusion criteria were invited to an infor- mative orientation session. Informed consent and baseline data were collected from interested individuals at orienta- tion; then, participants were randomized to either MBSR
(BC) or UC. Participants were asked to wear an actigraph on their nondominant wrist and complete a sleep diary for three continuous 24-h periods immediately following the baseline and follow-up assessments. This time frame was chosen in order to minimize participant burden and is in accordance with previous recommendations that actigraphic monitoring be conducted for at least 72 h [36,37]; in addition, it is consistent with previously con- ducted studies using actigraphy [38,39].
Demographics, clinical history, and assessments of subjective and objective sleep parameters were collected at baseline, post-treatment, and 12 weeks. Participants received an incentive of $30 for data completion at each time point.
MBSR(BC) intervention
The MBSR(BC) program was adapted for BCS from the MBSR program developed by Jon Kabat-Zinn and his colleagues [40,41]. MBSR(BC) teaches BCS to take an active role in stress reduction and symptom management through six, 2-h weekly sessions that include the following:
(i) educational materials related to relaxation, meditation, the mind–body connection, and healthy lifestyles; (ii) prac- tice of meditation, yoga, body scan, and walking medita- tion; and (iii) supportive group interaction and discussion [18,19]. MBSR(BC) participants were requested to formally and informally practice the meditative techniques for 15–45 min per day and to record their practice time during Figure 1. Flowchart showing recruitment and enrollment of the 79 subjects into the sleep supplement study; the 79 subjects completed the study and were included in outcome analyses
the 12-week study. Compact discs and a diary were provided to facilitate meditative practices and documentation.
UC control group
Participants in the UC group underwent normal post- treatment clinic visits and were asked to refrain from the practice of meditation, yoga techniques, and/or MBSR dur- ing the study, with reminders to refrain from these practices occurring at all assessment time points. The UC group was waitlisted to receive the MBSR(BC) intervention within 6 months of study enrollment.
Measures
Demographic and medical history data
Demographic and medical history data were obtained from participants through self-report questionnaires. Demographic data included age, ethnicity, educational attainment, and mar- ital, income, and employment status. Medical history data in- cluded type and dates of cancer diagnosis and treatments.
Objective sleep parameters
The Actiwatch® Score (Mini Mitter, Bend, OR, USA) actigraph was used to quantify OSP parameters. The actigraph uses an accelerometer to sense and record motion [42] and is a reliable and valid measure of sleep parameters in healthy adult populations [42,43]. Actigraphy scores agree with Electroencephalography sleep/wake status 95%
of the time [42].
Actigraphy has been used among cancer patients and provides good predictive validity of clinical outcomes (i.
e., survival and QOL). It is generally well tolerated and has estimates of compliance at 88% over a 5-day period [44]. Sleep parameters are measured by actigraphy in combination with patient recordings of bedtime and rising time. Information regarding bedtimes and rising times was manually inputted into the scoring program on the basis of participants’ self-reported bedtimes and rising times.
Actigraphy software then determined sleep and wakeful- ness using previously validated algorithms. In accordance with recommendations [45], sleep parameters were assessed using five measures: (i) latency to fall asleep (number of minutes to fall asleep); (ii) sleep efficiency (the percentage of time in bed spent sleeping); (iii) mi- nutes of wake after sleep onset; (iv) number of waking bouts; and (v) number of minutes asleep at night.
Subjective sleep parameters
The Pittsburgh Sleep Quality Index (PSQI) measured SSP and quantity on the basis of the participant’s recall of sleep patterns and behaviors during the past month [47]. The PSQI’s 19 questions measure seven domains of sleep: qual- ity, latency, duration, efficiency, disturbances, use of sleep
medications, and daytime sleep function [46]. Reliability of the PSQI ranges from 0.70 to 0.78 for sleep disturbance [47].
Sleep diaries
While wearing the actigraph, patients recorded in a diary the following: (i) time they went to bed; (ii) time it took to fall asleep, (iii) rising time; (iv) number of hours slept;
and (v) consequences of sleep difficulty (e.g., fatigue and depression). These diaries were designed by Carpenter for use in studying hotflashes and were modified by our team to be used with the actigraphy software to ensure accurate interpretation of data [48].
Statistical analyses
Student t-tests and chi-squared tests were used to compare baseline characteristics of the randomly assigned groups.
Analysis of covariance, adjusting for baseline values, was used to compare means scores of subjective and objective measures of sleep by random assignment. Analyses focused on comparisons from baseline to 6 weeks and from 6 to 12 weeks. Among participants assigned to MBSR(BC), Spearman correlation coefficients were calculated to examine the association between minutes of MBSR practice and change in SSP and OSP measures. A two-sided p-value of<0.05 was used to define statistical significance for all analyses.
Results Participants
Tables 1 and 2 describe baseline characteristics of the 79 participants. Participants randomized to the MBSR(BC) in- tervention (n = 38) did not differ statistically at baseline from participants randomized to the UC group (n = 41). The mean age of the sample was 57 years (SD = 9.7). Most participants (73.4%) were White non-Hispanic, had stage I or stage II BC (n = 54, 68.4%), and had a mastectomy (57%). Ten women (12.7%) received chemotherapy, 22 participants (27.8%) received radiation, 23 participants (29.1%) received both chemotherapy and radiation, and 24 participants (30.4%) underwent surgery without either adjunctive therapy.
For the subjective analysis (PSQI), 79 participants were assessed at baseline, 76 were assessed at 6 weeks, and 77 were assessed at 12 weeks. Seventy-eight participants completed the actigraphy measures at baseline because one person who worked nights was unable to use the device. Seventy-seven participants completed actigraphy measures at 6 weeks, and 72 completed at 12 weeks.
Effect of MBSR(BC) on SSP
Analysis of covariance results of MBSR(BC) on SSP over time are shown in Table 3. When examining changes from baseline to 6 weeks for the PSQI standardized total score, nearly all means favored the MBSR(BC) group (lower
mean scores at both time points). However, none of these differences reached statistical significance.
Effect of MBSR(BC) on OSP
Objective sleep/wake and activity/rest values from actigraphy assessments are displayed in Table 3. From baseline to 6 weeks, change in OSP did not differ by random assignment, although there was a counterintuitive
trend of longer wake periods in the MBSR(BC) group (61.3 min) versus UC group (51.4 min, p = 0.07).
Indications of a positive effect of MBSR(BC) on OSP were observed in the 6-week to 12-week objective assess- ments. From 6 to 12 weeks, there were statistically signifi- cant improvements in the MBSR(BC) group in actigraphy measures of sleep efficiency and number of waking bouts.
The magnitude of these differences was moderate. Sleep ef- ficiency, or the percent of time in bed actually spent asleep, Table 1. Baseline demographic characteristics of participants in the sleep supplement of a randomized controlled trial
Characteristic Total (n = 79) UC (n = 41) MBSR(BC) (n = 38) p-value Linear trend
Age, mean, years (standard deviation) 57.0 (9.7) 58.0 (10.2) 56.1 (9.1) 0.39
Race/ethnicity, n (%) 0.94
White, non-Hispanic 58 (73.4) 31 (75.6) 27 (71.0)
White, Hispanic 9 (11.4) 4 (9.8) 4 (10.5)
Black, non-Hispanic 8 (10.1) 4 (9.8) 5 (13.2)
Other single race/ethnicity 1 (1.3) 1 (2.4) 0 (0.0)
Multiple race/ethnicity 3 (3.8) 1 (2.4) 2 (5.3)
Cancer stage, n (%) 0.28 0.68
0 13 (16.5) 8 (19.5) 5 (13.2)
1 27 (34.2) 15 (36.6) 12 (31.6)
2 27 (34.2) 10 (24.4) 17 (44.7)
3 12 (15.2) 8 (19.5) 4 (10.5)
Type of breast cancer, n (%) 0.61
Lobular carcinoma in situ 3 (3.8) 1 (2.4) 2 (5.3)
Ductal carcinoma in situ 35 (44.3) 19 (46.3) 16 (42.1)
Invasive lobular 4 (5.1) 3 (7.3) 1 (2.6)
Invasive ductal 22 (27.8) 9 (22.0) 13 (34.2)
Not specified/unknown/other 15 (19.0) 9 (22.0) 6 (15.8)
Surgery type, n (%) 1.0
Lumpectomy 34 (43.0) 18 (43,9) 16 (42.1)
Mastectomy 45 (57.0) 23 (56.1) 22 (57.9)
Treatment type, n (%) 0.55
Chemotherapy 10 (12.7) 3 (7.3) 7 (18.4)
Radiation 22 (27.8) 12 (29.3) 10 (26.3)
Chemotherapy and radiation 23 (29.1) 13 (31.7) 10 (26.3)
Surgery only 24 (30.4) 13 (31.7) 11 (29.0)
Marital status, n (%) 0.72
Married 47 (59.5) 24 (58.5) 23 (60.5)
Divorced 7 (8.9) 3 (7.3) 4 (10.5)
Single 8 (10.1) 6 (14.6) 2 (5.3)
Widowed 12 (15.2) 6 (14.6) 6 (15.8)
Other 5 (6.3) 2 (4.9) 3 (7.9)
Education status, n (%) 0.30 0.33
High school or less 16 (20.2) 11 (26.8) 5 (13.2)
Some college/vocational 27 (34.2) 12 (29.3) 15 (39.5)
College and above 36 (46.6) 18 (43.9) 18 (47.4)
Income, n (%) 0.89 0.95
<$10,000 9 (11.7) 5 (12.5) 4 (10.8)
$10,000 to<$20,000 16 (20.8) 7 (17.5) 9 (24.3)
$20,000 to<$40,000 20 (26.0) 11 (27.5) 9 (4.3)
$40,000 to<$80,000 18 (23.4) 10 (25.0) 8 (21.6)
$80,000 to<$100,000 8 (10.5) 5 (12.5) 3 (8.1)
$100,000 or more 6 (7.8) 2 (5.0) 4 (10.8)
Employment, n (%) 0.54
>32 h/week 24 (30.4) 12 (29.3) 12 (31.6)
<32 h/week 5 (6.3) 4 (9.8) 1 (2.6)
Retired 29 (36.7) 16 (39.0) 13 (34.2)
Medical leave/disabled 7 (8.9) 4 (9.8) 3 (7.9)
Other 14 (7.7) 5 (12.2) 9 (23.7)
UC, usual care; MBSR(BC), mindfulness-based stress reduction for breast cancer survivors.
was 78.2% in the MBSR(BC) group compared with 74.6%
among the UC group (between groups Cohen’s d = 0.33;
p = 0.04). Additionally, the average number of waking bouts was significantly reduced in the MBSR(BC) group (93.5 versus 118.6, between groups Cohen’s d = 0.38; p < 0.01).
Effect of MBSR(BC) on diary data
Although means were in the expected direction, no statis- tically significant differences were observed in sleep diary data reports (Table 3).
Comparison of sleep diaries to actigraphy data
Sleep diaries confirmed sleep disruption among MBSR(BC) and UC groups. Sleep diary reports were largely similar to actigraphy data. TST for actigraphy and diary were signif- icantly correlated (r = 0.58; p< 0.001). Participants were less able to estimate how long it took them to fall asleep, with
actigraphy and diary accounts of latency not as strongly cor- related compared with other measures; however, the correla- tion was still significant (r = 0.28; p = 0.02).
MBSR(BC) adherence and sleep parameters
No statistically significant correlations were observed be- tween the amount of MBSR(BC) practice (of any type) and measures of sleep parameters. These results were con- sistent for minutes of practice of individual components of MBSR and combined practice.
Discussion
Our objective sleep (actigraphy) results indicated greater sleep efficiency and less sleep disturbance in MBSR(BC) participants compared with UC participants. These results are unique because very few studies have examined MBSR Table 2. Baseline objective and subjective sleep parameter characteristics of participants in the sleep supplement of a randomized controlled trial
Measure Characteristic Total (n = 79) UC (n = 41) MBSR(BC) (n = 38) p-value
Sleep outcome (mean ± SD)
PSQI Sleep disturbance 1.87 (0.65) 1.88 (0.56) 1.87 (0.74) 0.95
Sleep duration 0.57 (0.84) 0.59 (0.77) 0.55 (0.92) 0.86
Sleep dysfunction 1.04 (0.71) 1.02 (0.65) 1.05 (0.77) 0.86
Latency to fall asleep 1.46 (1.08) 1.39 (1.07) 1.53 (1.11) 0.58
Efficiency 0.80 (1.04) 0.90 (1.11) 0.68 (0.96) 0.42
Total score (standardized) 8.19 (4.36) 8.39 (3.63) 7.97 (5.06) 0.49
Actigraphy Latency to fall asleep (minutes) 25.4 (26.0) 26.3 (22.9) 24.4 (29.3) 0.75
Percent of time in bed sleeping 78.8 (7.6) 77.4 (7.3) 80.4 (7.7) 0.08
Minutes of wake after sleep onset 61.8 (28.0) 69.8 (30.8) 53.2 (21.7) 0.007
Number of waking bouts 94.1 (41.6) 101.8 (40.3) 85.7 (38.6) 0.08
Average activity non-rest periods 340 (124) 331 (139) 349 (105) 0.53
Minutes sleep at night 486 (71) 492 (78) 479 (62) 0.42
Sleep diary Sleep duration 7.09 (1.32) 7.04 (1.38) 7.15 (1.26) 0.55
Latency to fall asleep 34.2 (16.2) 30.9 (23.7) 37.7 (62.2) 0.63
UC, usual care; MBSR(BC), mindfulness-based stress reduction for breast cancer survivors; SD, standard deviation; PSQI, Pittsburgh Sleep Quality Index.
Table 3. Efficacy of MBSR(BC) program on subjective and objective sleep parameters
N
Adjusteda6-week mean (95% CI) Adjusteda12-week mean (95% CI)
UC MBSR(BC) p-value UC MBSR(BC) p-value
PSQI Sleep disturbance 79 1.63 (1.46, 1.80) 1.53 (1.35, 1.70) 0.38 1.68 (1.51, 1.85) 1.56 (1.38, 1.73) 0.59 Sleep duration 78 0.58 (0.40, 0.76) 0.44 (0.24, 0.63) 0.62 0.39 (0.22, 0.56) 0.31 (0.13, 0.48) 0.96 Daytime dysfunction 79 0.79 (0.58, 0.99) 1.02 (0.81, 1.24) 0.95 0.91 (0.71, 1.11) 0.91 (0.71, 1.12) 0.35 Latency to fall asleep 79 1.43 (1.20, 1.67) 1.19 (0.95, 1.43) 0.22 1.29 (1.05, 1.52) 1.1 (0.87, 1.36) 0.84 Efficiency 79 0.82(0.53, 1.10) 0.65 (0.35, 0.95) 0.89 0.73 (0.47, 1.00) 0.57 (0.30, 0.85) 0.90 Total score (standardized) 79 7.79 (6.59, 8.99) 7.37 (6.12, 8.62) 0.98 7.41 (6.26, 8.56) 6.91 (5.71, 8.11) 0.97 Actigraphy Latency to fall asleep (minutes) 77 31.9 (23.3, 40.5) 29.5 (20.6, 38.4) 0.07 43.2 (31.7, 54.6) 27.9 (16.5, 39.4) 0.10 Efficiency 77 77.5 (75.1, 79.8) 76.5 (74.1, 79.9) 0.32 74.8 (72.0, 77.5) 77.9 (75.2, 80.7) 0.04 Minutes of wake after sleep onset 77 51.4 (44.4, 58.8) 61.3 (53.9, 68.6) 0.07 60.5 (53.2, 67.8) 62.7 (53.4, 70.0) 0.24 Number of waking bouts 77 90.9 (79.5, 102.4) 100.3 (88.4, 112.2) 0.27 115.8 (100.6, 131.1) 96.8 (81.6, 112.1) 0.01 Minutes sleep at night 77 467 (448, 486) 482 (462, 501) 0.62 494 (473, 515) 494 (473, 514) 0.55 Sleep diary Sleep duration 79 6.93 (6.56, 7.29) 7.18 (6.80, 7.56) 0.65 7.13 (6.62, 7.45) 7.26 (6.86, 7.67) 0.40 Sleep latency 79 33.1 (21.5, 44.6) 28.9 (16.9, 40.9) 0.31 27.9 (19.9, 35.93) 24.2 (15.9, 32.5) 0.54 UC, usual care; MBSR(BC), mindfulness-based stress reduction for breast cancer survivors; PSQI, Pittsburgh Sleep Quality Index; CI, confidence interval.
aAdjusted for baseline values.
using OSP. Objective actigraphy data were consistent with one noncancer population study [33]. When MBSR was compared with eszopiclone pharmaceutical therapy, improvements were found in both groups, and the MBSR group had a shorter latency to sleep onset [33]. In contrast to ourfindings, MBSR was not found to improve measures of OSP in a nonrandomized study of 70 adults [34] or adolescents (p = 0.06) Thus, to our knowledge, our study provides the strongest empirical support for a positive rela- tionship between MBSR(BC) and OSP improvements.
Although not statistically significant, SSP results tended to be in the direction of improvement following MBSR(BC).
These trends were in a consistent direction with previous studies. For example, Andersen et al. [20] found improve- ments from baseline to post-MBSR intervention in sleep disturbance and sleep problems among BCS, and our team’s previousfindings of improved drowsiness and sleep distur- bance among 84 BCS [19]. Other studies demonstrating beneficial effects of MBSR on sleep included the following:
(i) Carlson et al. [22], who found improved subjective sleep duration and efficiency with the use of MBSR among breast and prostate cancer patients; (ii) Carlson et al. [24], who found improved self-rated sleep parameters among BCS;
and (iii) Carlson and Garland [23], who found reduced inci- dence of sleep disturbances. The potential and proposed mechanism of action of MBSR(BC) on improvement in sleep parameters is thought to occur through self-regulation processes of focused awareness and attention, diminished emotional reactivity to negative states, and increased accep- tance of experiences without judgment and non-elaborative awareness of thoughts, feelings, and sensations [49,50].
Improved self-regulation of emotional bias and increased openness to the current experience often decreases rumina- tion over fears of recurrence that plague BCS. All these pro- cesses may contribute to improvements in falling asleep, staying asleep, and undesired waking.
Potential clinical significance
Although there were few statistically significant results, our findings suggest the potential of MBSR(BC) for clinically meaningful improvements in sleep parameters, particularly for improvement in objective sleep quality. This is tentatively prefaced by the context that the BCS enrolled in this study had a reasonably good sleep efficiency overall, which may have created a potential ceiling effect and also there could be a consideration that this was due to chance. Future studies should continue to further evaluate the magnitude of these effects, particularly among cancer survivors with substan- tially impaired sleep function (e.g., advanced stage cancer survivors and also among survivors who are on treatment).
Thus, although we have identified that MBSR(BC) offers some nonpharmacological beneficial effects for sleep prob- lems among BCS, whether it is a treatment for insomnia remains yet to be determined.
Limitations and directions for future research
Although restricted to BCS, our sample was heterogeneous in terms of types of treatment (i.e., radiation and/or chemo- therapy) and time since treatment completion. Actigraphy may underestimate sleep latency and overestimate TST.
Also, having performed actigraphy monitoring for 72 h in order to limit participant burden leads to the potential to be adversely affected by one night of good or poor sleep and may not be entirely representative. Type 1 error may have been a concern because of multiple outcome compari- sons. These concerns were somewhat mitigated by two characteristics of the results: (i) the direction of both signif- icant and nonsignificant results was in a consistent direction, and (ii) these results were in the hypothesized direction. Re- garding type 2 error, the relatively small sample size may have negatively impacted statistical power. Another poten- tial reason for type 2 error was ceiling effects. With sleep ef- ficiency scores close to 80%, participants in both groups started the study with relatively good sleeping habits. These high baseline values may have decreased the study’s sensi- tivity to detect small effects and may have constrained the size of the effects observed as statistically significant. Also, 12 weeks may not be sufficient to test whether improve- ments resulting from MBSR(BC) can be sustained for longer periods. For the future, a longer, larger trial is recom- mended, either 6 months or 1-year post-intervention.
Future study needs to be completed on the benefits of for- mal versus informal MBSR practice to determine if a specific meditation technique is more beneficial for sleep improve- ment. Furthermore, the modest associations that we observed between subjective and objective measures of sleep indicate the need for improved outcome measurement, including both self-report and objective measures of sleep. Specifically, the results of this study support the need for further examination of objective assessment of sleep through actigraphy and, more specifically, the identification of other reliable and valid sub- jective sleep measurements instruments that may be sensitive to cancer survivors. Future recommendations are to explore the relationship of biological mechanisms associated with improvements in objective and subjective sleep parameters.
Conclusions
In addition to the established effects of MBSR(BC) in reduc- ing psychological and physical symptoms in BCS, this ran- domized controlled study provided evidence that MBSR (BC) favorably influences sleep as measured by actigraphy.
Acknowledgements
The project described was supported by award number 3R01CA131080- 02S1 from the National Cancer Institute. The content is solely the respon- sibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health. This study protocol was approved by the institutional review board at the University of South Florida to ensure the ethical treatment of participants.
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